Color formers for producing yellow dye images by color development



United States Patent Ofitice 3,ll56,674 Fatented Oct. 2, 1952 3,056,674 COLOR FORMERS FOR RODUCING YELLOW DYE IMAGE BY (IULQR DEVELOPMENT Walter F. Hotfstadt, Vestal, and Alex P. Altavilla, Johnson City, N.Y., assignors to General Aniline & Film Corporation, New York, N.Y., a corporation of Delaware No Drawing. Filed Feb. 1, E61, Ser. No. 86,281 4 Claims. (Cl. 96-55) This invention relates to color photography and the formation of colored photographic images by color forming development. More particularly, the invention relates to the production of yellow photographic images, to certain color formers for producing such images and to silver halide photographic emulsions containing the color formers.

It is well known in the art to produce colored photographic images by reacting imagewise quantities of the oxidation products of a primary aromatic amino developing agent with a color forming component or a color coupler. Present day multilayer color packs are based on these color forming reactions. In fabricating a multilayer photographic element, a typical construction calls for three contiguous layers which are individually sensitired to a different primary color aspect. Thus, one layer responds to red rays, the second layer to green rays, and the third layer to the blue rays. After exposure, the film is color developed with a primary aromatic amino developing agent whereby subtractively colored images are formed in each layer, the intensity of which is inversely proportional to the exposing radiation. By this procedure, a cyan image is obtained in the red sensitive layer, a magenta image in the green sensitive layer, and a yellow image in the blue sensitive layer. When these subtractively colored images are viewed through white light in superimposition, there is rendered a colored reproduction of the subject being photographed.

For obtaining the cyan images, it is the common practice to utilize a phenol or phenolic type of compound, such as a naphthol. For a magenta image, pyrazolones are frequently employed, whereas the yellow image is formed from an a-arylacetanilide structure. It is this latter representative of color formers with which the present invention is concerned.

Yellow color forming components of the type derived from an c-arylacetanilide can be formulistically depicted as follows:

It is to be noted that couplers of this type embody a reactive methylene grouping, i.e., a structure characterized by the presence of a methylene bridge linked to various negative groupings which, in the above formula, are keto functions located on either side of the methylene bridge. It is the methylene portion of the coupler, the hydrogen atoms of which are acidic by virtue of the electron-attracting keto functions, which couples with the oxidized primary aromatic amino developing agent to produce the colored dye images.

Since the advent of color photography based upon color development first proposed by Rudolph Fischer in 1912, considerable effort has been expended in refining the system. Much of this work, which is documented in various photographic publications and patents, is directed to improving the stability of colored photographic images, particularly to the action of such agencies as light and conditions of excessive humidity. Since the dye images are formed from the coupling components, it follows that the latter entities must also be stable in the photographic emulsion. For instance, the coupler and the dye image produced therefrom must not be decolorized or otherwise altered when subjected to the various steps or stages of the color development process. It is furthermore essential that the dye image exhibits the proper spectral and optical quality; cheapness and ease of manufacture of coupler components are also important factors.

in general, there are two methods whereby color couplers are incorporated in a silver halide photographic emulsion. In one system lipophilic color formers are dissolved in high boiling water-immiscible solvents and the resulting oily solution is then dispersed throughout the photographic emulsion. Another system, which finds commercial utilization, depends on the use of a hydrophilic color former, that is, color formers which are soluble in dilute alkali. These solutions can be mixed or otherwise combined with the silver halide emulsion. Both systems have various advantages and disadvantages. For instance, it is ordinarily much simpler to dissolve a coupler in dilute alkali for combining with the photographic emulsion than resorting to the solvent system. However, the latter procedure requires the use of relatively expensive and complex homogenizing equipment in order to form a line dispersion of the coupler throughout the emulsion. On the other hand, the dye images derived from hydrophilic color formers tend to be less stable than the images produced from the lipophilic couplers. There are also certain minor differences which distinguish these two systems of incorporating couplers in photographic emulsions. Such information can be procured from the various technical journals and patents on color photography.

We have now discovered a new type of color former for producing yellow dye images which represents a marked improvement over yellow color forming compo nents heretofore known to the art and the provision of this yellow color forming component constitutes a primary object of this invention. Other objects and aims will be apparent as the description proceeds.

In accordance with this invention, there is proposed a new and improved color forming component for forming yellow images in which the said coupler is represented by the following general formula:

( COOM;

wherein R is a higher alkyl group having from 8 to 20 carbon atoms, the purpose of which is to prevent wandering or difiusion of the color forming compounds throughout the emulsion layer with concomitant color degradation. Suitable alkyl moieties for this purpose include alkyl groups such as octyl, nonyl, decyl, undecyl, tetradecyl, octadecyl, eicosyl and the like; M and M which may be alike or different can be hydrogen or a carboxylic acid salt such as an ammonium salt including amine salts, alkali metal salts, i.e., lithium, potassium, sodium, etc. The designation of M and M will depend to some extent on the pH of the emulsion in which the coupler is incorporated. Thus, the coupler may be added in the form of its alkali metal salt to the emulsion which, after the coating operation, may be subjected to conditions of lower pH causing the coupler to be converted to its acid form. It is to be understood, therefore, that the coupler structures as herein described are not limited to any particular salt or free acid form.

A novel feature of the couplers as described herein for producing yellow dye images on color development is the presence of a carboxylic acid function on the para-position of the benzoyl grouping. That this particular structural modification has heretofore been unknown to the art is indeed not surprising. Normally such structures would be synthesized by reacting a p-carboxylbenzoyl acetic ester with an aniline to form a benzoyl acetanilide. However, because of the unavailability of p-carboxylbenzoyl acetic ester, this reaction is not suited for producing color former structures of the benzoyl acetanilide type wherein the benzoyl grouping contains a carboxylic acid function particularly in the para-position thereof. We have, for instance, searched such well known chemical references as Beilstein and Chemical Abstracts and found no mention of the aforesaid p-carboxylbenzoyl acetic ester. Manifestly, the prior art has not previously contemplated our coupler structures. It has now been discovered most unexpectedly that a benzoyl acetanilide yellow coupler containing a para-cyano group can be effectively hydrolyzed in alkaline media to the corresponding carboxylic acid structures. The reaction can be carried out by refluxing the aforesaid cyano coupler in benzoylacetanilide in alcoholic potassium hydroxide for several hours. That the couplers should survive this energetic alkaline treatment without other locations or sites of the couplers structure being attacked by the strong alkaline hydrolyzing agents is unusual and unpredictable and also accounts for the fact that the reaction was not, until the present, utilized by skilled artisans as a route to arriving at p-carboxybenzoylacetanilide coupling components. It is submitted that this rugged characteristic of the paracarboxylbenzoylacetanilide coupler contributes substantially to the highly stable yellow dye images produced from these couplers on color forming development. A possible theory to account for such stability is the relatively high electronegativity of the carboxyl group when situated in the para-position of the benzoyl group, an environment in coupler structure heretofore not occupied by a carboxyl function. There have, of course, been yellow color formers produced wherein twin carboxylic functions occur within the same molecule (but such prior art configurations were incapable of yielding on color forming development, yellow dye images), having stability approaching that possessed by our color former structures. Aside from giving rise to exceedingly stable dye images, the color couplers of the invention, because of the twin carboxylic acid functions are much more soluble than couplers having a single acetic function of the group. This is an advantage when dissolving the couplers in an alkaline medium for subsequent incorporation in a light sensitive photographic silver halide emulsion.

In general, we prepare our novel yellow color couplers by reacting a p-cyanobenzoylacetic ester with a 4-allcoxyl- 3-aminobenzoic acid whereby is formed a 2-alkoxyl-5'- carboxy-2-p-cyanobenzoylacetanilide. On alkaline hydrolysis, the cyano group is converted to a carboxylic function with concomitant formation of a dicarboxylic benzoylacetanilide which is the basic structure of the yellow color formers as described herein.

In the following list are formulistically depicted in the form of their free acids, the various color former structures falling within the ambit of general Formula II.

COOH

OCroHn COOH (4) o 0 on O C12H25 I00 OH HO 0 o -fil-CHz(H3NH- O 0 OH O Cis ar G 0 OH no 0 o o-orno-Nn- H II a) C 0 OH HO 0 0O fl3ornfi rrn- 0 CmHav (9) Co OH O CmHaQ In the following examples are presented specific methods for preparing the color formers of this invention. It

is to be understood, however, that these examples are given by way of illustration only and are not be construed as limiting or narrowing the metes and bounds of the invention.

EXAMPLE I 5 -Carb0xy-2-p-Carb0xybenzoyl-2-T etradecoxyacetanilide C O OH ii i no 0 (IQ-COHzClNlI-Q 2 g. of 5-carboxy-2-p-cyanobenzoyl-2-tetradecoxyacetanilide was refluxed in a solution of 10 g. of potassium hydroxide in 50 ml. of ethanol for several hours or until the evolution of ammonia had ceased. The reaction mixture Was poured into an ice-hydrochloric acid mixture and the resulting white solids collected by filtration and Washed with cold water. The filter cake was triturated with hot acetonitrile. cooled and filtered. The yield of white product was 1.0 g. and did not melt below 230 C.

The 5-carboXy-2-p-cyanobenzoyl-2-tetradecoxyacetanilide was prepared as follows: Into a 250 ml., 3 necked flask, equipped with a stirrer and an upright steam heated condenser were placed 17.5 g. of 3-amino-4-tetradecoxybenzoic acid (0.05 mole) and m1. of dry xylene. The mixture was heated to reflux and 13.1 g. of ethyl-4-cyanobenzoyl acetate (0.055 mole) added. The reaction was then heated under reflux with stirring for 2 hours. After cooling, the crystalline solids were collected by filtration and washed with xylene. The resulting filter cake was recrystallized from about 300 ml. of acetic acid. The yield of White product was 18 g. (69%) M.P.=173174 C. N=Calc.=5.38%. Found=5.49%.

The ethyl-4-cyanobenzoy1 acetate was prepared by reacting 4-cyanobenzoyl chloride with acetoacetic ester in the presence of sodium methylate. Hydrolysis of the resulting ester complex with a mixture of ammonium chlo ride and ammonium hydroxide yielded the ethyl-4-cyanobenzoyl acetate. After one crystallization from alcohol, the purified product melted at 836 C. The preparation of benzoylacetic esters as described herein is patterned after the method published by Thorp and Brunskill in J.A.C.S. 37, 1261.

The 4-cyanobenzoyl chloride-M.P. 73 C.--was obtained by acylating the free acid with phosphorous pen tachloride utilizing the method of Scholl and Neuberger M, 33, 517. The 4-cyanobenzoic acid was produced by the diazotization of p-aminobenzoic acid followed by treating the resulting diazonium salt with cuprous cyanide (Sandmeyer reaction). The preparation was modeled after the method disclosed by Valby and Lucas in J.A.C.S., 51, 2719 (1929).

The preparation of this yellow coupler was patterned after the procedure used in the first example except that the 3-amino-4-tetradecoxybenzoic acid of the earlier example was replaced by the corresponding octadecoxy derivative.

EXAMPLE III In this preparation 3-amino-4-octoxybenzoic acid was condensed with 2-p-cyanobenzoyl acetic ester followed by alkaline hydrolysis of the cyano function. The results paralleled those of Example I.

The color couplers contemplated in the instant invention can be incorporated in a photographic light sensitive silver halide emulsion in the manner well known to the art. For instance, the coupler can be dissolved in an aqueous alkaline solution which is then blended with the silver halide emulsion and the mixture then coated on a suitable photographic support or base. The coupler can be dissolved in any suitable alkaline solution capable of forming soluble salts with the carboxylic functions of the coupler. In general, we have ascertained that aqueous or alcoholic solutions of organic bases including ammonium hydroxide, alkali metals are especially suitable for this purpose. The choice of alkali to effect solution of the coupler is unimportant since it is the coupler structure per se which accounts for the highly desirable photographic properties previously enunciated. It is, of course, manifest that no alkaline solubilizing medium should be chosen which would be damaging or deleterious to the photographic emulsion in which the coupler is to be incorporated.

Typically, one gram of the color former of Example 1 was dissolved in about 20 milliliters of water containing sufficient sodium hydroxide to impart the solution a pH at about 7.5. The solution was combined with a silver bromide emulsion and the mixture coated on a suitable base such as triacetate filmbase. Upon exposure and development in a color developer containing as the active principal N-ethyl-N-hydroxyethyl-p-aminoaniline there was obtained a brilliant yellow dye image having an absorption maximum at 428 mu.

On exposing the aforedescribed yellow photographic image to conditions of excessive humidity and high light intensity, it was found to undergo degradation to a much lesser degree than typical benzoyl acetanilide structures heretofore known. The couplers as described herein must provide the photographic art with highly stable yellow dye images produced from hydrophilic or alkali soluble color formers and it is submitted that this is a significant advance in this area of the photographic field.

Modification of the invention will occur to persons having skill in the art to which they pertain. For instance, although it is a common practice to incorporate color formers in gelatin layers, the couplers of the invention can be blended with other photographic colloids and in this connection mention is made of synthetic resins such as polyvinyl alcohol, carboxymethyl cellulose, starch, gum arabic, casein, zein, etc. Furthermore, any of the color developers used in the formation of quinoamine and azo methine dyes by color forming development may be employed. We, therefore, do not intend to be limited in the patent granted except as necessitated by the appended claims.

We claim:

1. A light sensitive silver halide photographic emulsion containing a non-diffusing coupler compound of the following formula:

COOM

H r s-Q wherein M and M are each selected from the class consisting of hydrogen and ammonium group and the alkali metals and R is a higher alkyl group of from 8 to 20 carbon atoms.

4. The process as defined in claim 3 wherein the color former is 5 carboxy-Z-p-carboxybenzoyl-2-tetradecoxyacetanilide.

MOOO

References Cited in the file of this patent UNITED STATES PATENTS 2,425,503 Bavley Aug. 12, 1947 2,694,008 Berger et a1. Nov. 9, 1954 2,875,057 McCrossen et a1. Feb. 24, 1959 FOREIGN PATENTS 334,344 Switzerland Ian. 15, 1959 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION October 2, 1962 Patent No" 3,056 674 Walter Fa Hoffstadt et al.,

or appears in the above numbered pat- It is hereby certified that err d Letters Patent should read as ent requiring correction and that the sai corrected below.

Column 6, line 36, for "5-" read 5 Signed and sealed this 20th day of August 1963 (SEAL) Attest:

DAVID L. LADD Commissioner of Patents ERNEST W. SWIDER Attesting Officer 

3. THE PROCESS OF PRODUCING A YELLOW DYESTUFF IMAGE IN A SILVER HALIDE EMULSION WHICH COMPRISES EXPOSING SAID EMULSION TO LIGHT AND DEVELOPING THE SAME WITH A PRIMARY AROMATIC AMINO DEVELOPER IN THE PRESENCE OF A COLOR FORMER FOR YELLOW HAVING THE FOLLOWING STRUCTURAL FORMULA; 